This invention relates to an anti-theft system employing threaded fasteners, and more particularly concerns specially modified threaded fasteners and an associated matching torque-producing driving tool in a lock-and-key relationship.
Electronic instruments of various types are generally installed in aircraft, boats and automotive vehicles as accessory equipment not originally incorporated during manufacture of the aircraft, boat or automobile. Such equipment is generally of modular configuration, adapted to be easily installed adjacent the pilot or driver. However, because of the often considerable value of such equipment, and the relative ease of mounting and removal, the equipment is at high risk of theft.
The installation techniques generally utilize machine bolts which engage receiving holes in the aircraft or vehicle or engage a rotatable locking latch built into the modular equipment. In the case of aircraft, instrument installatins are generally accomplished using bolts having a hexagonally shaped recess in their head, said bolts generally being called Allen bolts. In the use of Allen bolts for installation of modular equipment into aircraft cockpit panels, the head of the bolt is usually disposed in spaced apart relationship with respect to an overlying protective panel, and may in fact reside within a receiving channel extending from said protective panel. In either event, the head of the Allen bolt is generally not accessible except by the long-stemmed portion of an L-shaped Allen wrench whose hexagonal shaft closely seats within the recess of the head of the bolt. Such manner of mounting, however, is little deterrent to a thief.
Threaded fasteners having heads of special configuration which can be engaged only by a turning tool of matching configuration have been described in U.S. Pat. Nos. 2,248,695; 3,073,206; 1,188,305, 3,673,912; 3,872,904; and elsewhere. Such fasteners and their matching turning tools function is the manner of a lock and key principle because the fastener can be tightened or loosened only by the matching torque-producing turning tool. Bolts utilized in a lock-and-key relationship are effective only when a great number of specialized configurations are possible, as in the case of keys utilized for tumbler locks. However, the cost of fabricating short production runs of bolts having various head configurations is prohibitively high.
It is accordingly an object of the present invention to provide a locking system comprising a threaded bolt and a matching turning tool to thwart unauthorized removal of modular equipment installed in aircraft, boats, automobiles and the like.
It is another object of this invention to provide a system as in the foregoing object capable of providing a lock-and-key principle of security and versatility.
It is a further object of the present invention to provide a system of the aforsaid nature amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.